Increases in weight gain among US children related to the childhood obesity epidemic may result in alteration of normal patterns of childhood linear growth and development. Few studies have evaluated the impact of weight gain on linear growth patterns or the relationship of linear growth with pubertal timing for a population- based sample of US children followed longitudinally. Using data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development, a comprehensive study which collected longitudinal growth and puberty measurements on a population-based cohort of children of diverse socioeconomic status from birth to age 15 years, this proposal provides an unprecedented opportunity to evaluate the following specific aims: Aim 1: To evaluate the association of early childhood (ages 2 -7 years) BMI increases with height gain during early childhood (ages 2-7 years) and how this association varies by gender. Aim 2: To evaluate the association of early childhood (ages 2 -7 years) BMI increases with the timing and magnitude of the adolescent growth spurt (peak height velocity) and height gain during adolescence (ages 9 - 15 years) separately for boys and girls. Aim 3: To evaluate the relationship between timing of height takeoff and peak height velocity with puberty separately for boys and girls. Aim 4: To assess the % of children in the population classified as early, average, and late maturers, based on their individual height velocity curves, and to compare BMI z-scores, increases in BMI during early childhood, and proportion overweight and obese, between early, average, and late maturers for boys and for girls. Results of the proposed study will offer an improved understanding of the relationship between weight gain in early childhood and alterations in patterns of linear growth, as well as the relationship between linear growth patterns and pubertal timing. This information is critical for ensuring accurate interpretation of childhood growth patterns in clinical practice, as well as for offering important insights into mechanisms of childhood linear growth and development. PUBLIC HEALTH RELEVANCE: The epidemic of childhood obesity among US children may result in alterations of normal patterns of childhood linear growth and development. Studies to evaluate the impact of weight gain and obesity on childhood linear growth and development will have practical implications regarding interpretation of the etiology of children's growth patterns, as well as theoretic implications regarding the potential mechanism of excess adiposity in driving growth and development.